Device responsive to changes in density of liquids



June 1, 1943. CROFT 2,320,720.

DEVICE RESPONSIVE TO CHANGES IN DENSITY OF LIQUIDS Filed July 19, 1941 2 Sheets-Sheet l I George/M Crof'f 7 G. M. CROFT,

Jun 1, 1943.

DEVICE RESPONSIVE TO CHANGES IN. DENSITY LIQUIDS Fild July 19, 1941 2 Sheets-Sheet 2 Georg/M. C'rol f W M/Qfi A ,4

Patented June 1, 1943 UNITED STATES PATENT OFFICE DENSITY 0F LIQUIDS George M. Croft, Pittsburgh, Pa,

Blaw-Knox Company, Pittsburgh, Pa., a corporation of New Jersey Application July 19, 1941, Serial- No. 403,151

testing them'out outside would not be practicable 2 Claims.

This invention relates to devices responsive to changes in density of a liquid and more especially to a device in which the changes in density of a liquid within an enclosure may be observed or used for control pu poses.

In carrying out various chemical and physical processes in which liquids are involved, it often is desirable to maintain a liquid contained in or flowing through a system in a nearly uniform condition of concentration, or to regulate the processes by the addition or removal of materials proportional to certain physical or chemical constituents in the treating liquid. In such cases it is important that variations in the liquid composition or the concentration of dissolved constituents therein shall be used for regulating purposes.

Under certain conditions where the treating liquid is a simple solution the concentration of the solute in the solvent may be the variable in accordance with which it is desirable to effect regulation; and in many cases such variation results in variability of the specific gravity of the solution and may be ascertained or registered by a hydrometer.

An object of this invention is to provide means by which a hydrometer in a liquid in a fully enclosed vessel, which may be under great or small pressure, may be used for automatic regulation of some process. The nature of the processes tobe regulated'or the mechanism of said regulation is not specific to theinvention and such processes will not be described herein, but a case may be cited by way of illustration.

In my Patent 2,266,959, entitled "Gas dehydration," I have described and illustrated apparatus in which the concentration of an aqueous solution is regulated by circulating a portion of the solution through an evaporator, where substantially uniform temperature and pressure and consequently a substantially uniform vapor pressure are maintained. If, in that process, the solution is one in which the specific gravity at constant pressure and temperature varies with the concentration, this device could be used to replace the temperature regulating devices described in that application. Other uses for the device, will be apparent to those familiar with the various chemical arts and industries.

A hydrometer which floats freely at the surface of a liquid furnishes a sensitive and very reliable means of indicating the density of the liquid. A hydrometer can be advantageously used for liquids in open vessels, but a procedure which would require the removal of samples and assignor to for an enclosed liquid, such as liquid carried by pipes and particularly at pressures other than atmospheric.

Attempts to use floats to register changes in density of liquids within enclosures have not been entirely satisfactory because of the requirements of mechanism actuated by the float which is subject to friction, sticking or other accidental derangements.

In measuring the density of a liquid in an enclosed system, I provide a chamber through which the liquid flows and which has an air or gas pocket into which the freely floating hydrometer may project abbve the surface of the liquid. The position of the hydrometer is observed through a window or windows, preferably by means of a so-called "electric eye or photoelectric cell system which may be used for operating any suitable control. Since the hydrometer operates in a closed gas or'air chamber above the liquid, the liquid may be subjected to pressures or changes of pressures above and below atmospherlc. Since the hydrometer is freely floating, an exceedingly sensitive and absolutely reliable indication can be obtained continuously and at all times and difllculties with friction, sticking of contacts, etc., which Further novel features and advantages of the invention will become apparent during the following detailed description of the present preferred embodiment outlined above which lsshown in the accompanying drawings. In the drawings:

Fig. 1 is a sectional view taken on a vertical axial plane through the illustrated embodiment of my invention;

Fig. 2 is a horizontal sectional view with parts in plan, taken on the Fig. 1; line 1-1 of Fig. 2 indicates the which the section of Fig. 1 is taken;

Fig. 3 is a partial section taken along the plane plane on of line I]IIII of Fig. 1;

are inherent in float- I operated control systems, are obviated.

plane of line 1I-]I of a bottom plate l5 and a cover or cap l6. An over-flow cup I1 is disposed within the chamber l3 and is supported on a pipe l8 extending through the bottom thereof, being welded thereon. The pipe I8 is slidable through a packing gland l9 welded in a suitable opening in the bottom plate L... The lower portion of the pipe I8 is threaded as at and extends through a suitable hole in a bearing yoke 2|, the upper ends of which are welded to the base I l. Adjusting nuts 22 on the threaded portion 20 of the pipe [8 permit the latter and the cup I'I to be adjusted vertically.

The lower end of pipe I8 is connected by suitable piping to the pipe or tank or other part of the system containing the liquid the specific gravity of which is to be determined. An

outlet 23 welded in a hole in the bottom plate I! of the float chamber is connected to a return line. By these connections, liquid flows through the pipe l8 into the over-flow cup l1 and, when the latter is filled, runs over into the float cham-' ber proper and out through the outlet 23. A slight pressure differential, of course, must be maintained between the inlet pipe l8 and the outlet 23 in order to cause circulation of liquid through the chamber l3. This may be provided by any suitable means such as a pump, or'by gravity. The gas pressure within l3 may be as high or as low as required by the process in connection with which the device is used. A pipe line 24 extending from a port 25' welded in'the tubular body l4 preferably communicates with a source of gas under a pressure equal to that at the'surface of the liquid in the float chamber. Trapped air in the chamber l3 may act in the same manner as an air cushion in a water line and make it unnecessary to provide a separate source of gas under pressure.

A freely floating hydrometer 26 is disposed within'the over-flow cup l1 and has a stem 21 freely slidable through a perforated guide disc 20 positioned in the cup near-the top thereof.

A baille 23 is disposed between the hydrometer and the bottom of the cup, being supported on legs 33. to prevent the flow of liquid from the pipe l3 into the cup I! from disturbing the position of the hydrometer.

The hydrometer may be observed directly or used to operate electrical control devices of any with the light source 32 and light-sensitive device 34 of the other eye.

Fig. 3 illustrates the structure of the ports 36 and 31, 36' and 31'. As there shown, each port comprises a short length of tube 33, the inner end of which is welded into a suitable openin in the tubular body l4 of the float chamber. The outer end of the tube 38 is threaded to receive a screw cap 39 havingan opening therein. A window 4| of transparent material is disposed between sealing gaskets 42 and is clamped against the end of the tube 38 by the overhanging outer end of the cap 39. It will be apparent that this construction provides sealed windows wnereby light beams may be caused to pass through the float chamber l3.

The hydrometer 26 is provided with a screen 43 which may conveniently be a light'cup or cylfinder of sheet metal .or other suitable material mounted on the upper end of the stem 21. The

screen is so positioned on the stem and of such length that in an intermediate position it will intercept enough light from reaching both cells 34 to prevent either from operating. The elevasuitable type. For such purpose I employ electric eyes of known construction. mounted on th outside of the body portion l4 of the chamber l3 by means of an annular supporting plate 3| welded thereto. Each eye comprises a light source 32 mounted on a post 33 and a lightsensitive device-34 mounted on a post 35, the posts- 34 and 35 being threaded for'vertical adjustment on the plate 3| by nuts thereon.

Each source 32 may conveniently comprise an incandescent lamp enclosed-in a suitable housing, as shown in Fig. 4, and each light-sensitive device 34 may comprise a photoelectric cell similarly enclosed within a suitable housing. The details of the parts of the eyes are not material to the present invention and any type of such device as is commercially available may be used.

The body portion l4of the float chamber has ports or windows 33 and 31 disposed in substantially diametrical opposition and in line with the source 32 and device 34 of one of the eyes. Similar ports 38' and 31' are positioned generally at right angles to the ports 33 and,

31, at a level below the latter, and in alinement' a gravity of the liquid.

tion of the cup I1 is adjusted so that its overflow level will be such that the float will poise at this medial position when the specific gravity of the liquid is at the desired average value. If the specific gravity of the liquid increases sufficiently the hydrometer will rise, permitting light through 36' and 3'|'- to actuate one o! the photoelectric cells; while if the specific gravity of the liquid diminishes, light through 36 and 31 will actuate the other photoelectric cell. It is obvious that by proper proportioningand adjustment the range in specific gravity of liquid between actuation of the respective cells may be direct reading through the windows, if a suitable scale is mounted in the chamber [3.

Fig. 4 is a diagrammatic illustration of an elec- V tric circuit whereby the device may control either an indicator or means to regulate the specific 44 indicates a control device, such as a valve, which may control mechanism for controlling the specific gravity of the liquid. For example, the valve 44 may be the valve in the gas supply to the boiler which is employed to evaporate water and thereby restore the specific gravity of a brine solution in the system of my Patent 2,266,959. The control device 44 is provided with solenoids 45 and 46 for operating it from one position to another, These solenoids are energized by the output of amplifiers or electronic valve systems 41 and 43, each of which is controlled by one of the photo-- electric cells 34. The control device is preferably of such construction that it remains in the position to which it was last actuated until it is positively actuated to its other position. Where the device 44 controls apparatus for restoring the desired density of a liquid as, for example, by controlling the gas supply of a burner for an evaporator which removes water and thereby increases the density or concentration of a brine,

the hydrometer 28 will rise when the desired density is restored and interrupt the light beam to the upper photoelectric cell and render the cell non-conducting and deenergize the solenoid 45. The lower photoelectric cell is then fully exposed and strongly illuminated and becomes conducting, so that the solenoid 46 is energized to operate the valve 44 and shut off the gas supply to the burner. As the brine then becomes di- 45 to open the valve 44 to cause the evaporator to regenerate the brine. While I have mentioned one application of my device as controlling the regeneration of a brine, the device may be employed to efiect other types of control whereby the liquid may be kept at a predetermined desired density or the device may control indicating instruments which indicate or record changes of density without serving to control the density of the liquid.

The adjustability of the over-flow cup I! makes it possible to vary the specific gravity of the liquid at which the device 44 will be operated. In other words, the higher the cup I I is adjusted, the lower the specific gravity at which the device M will be operated by the control device I and vice versa.

In Figs. and 6 are shown, respectively, a plan view and elevation showing a modification in which a mirror 10!! is carried on the hydrometer stem. The mirror, instead of interrupting the light beam, reflects the beam from a light source lfll to a photoelectric cell I82. When such a device is employed a single window through the chamber walls may-be sufiicient. As shown in Fig. 6, the mirror, when the hydrometer 26 is in its upper position, reflects the light .from the source 59!, to an upper photoelectric cell I02 and when in its lower position reflects the light from a lower light source ml to a lower photoelectric cell i922 to eflect a control like that illustrated in Fig. 4. While it is preferred that the light source and photoelectric cells be on the outside of the hydrometer-containing chamber and the position of the hydrometer be viewed through windows, the light sources, the photoelectric cells, or both. may be within the enclosure It will be apparent from the foregoing description'and explanation that the invention provides a sensitive and reliable device responsive to the density or specific gravity of a liquid which may be in an enclosed system and by an enclosed system I mean one in which the liquid may be par= tially or fully enclosed, as distinguished from a liquid in an open vessel: The liquid in an enclosed system is generally at a pressure above or of the liquid in an v closed chamber,

below atmospheric, and the device of the present invention will operate satisfactorily for liquids under high pressure, such as those of several thousand pounds per square inch. Although the hydrometer is completely enclosed and may be subjected to any desired pressure, the regulating devices actuated byit may be entirely outside oi the enclosure and all adjustments may be made without access to the interior of the enclosure. The hydrometer is freely floating. Since the light beams in no way interfere with the free movement of, the hydrometer, the device is very sensitive and reliable and not subject to mechanical difllculties encountered in the operation of valves, electric switches, etc., by means offloats.

While I have illustrated and described .the preferred embodiment of my invention, it is to be understood that the invention may be otherwise embodied and practiced within the scope of the following claims.

I claim:

1. A device responsive to. changes in the density of liquid in an enclosed system, comprising a an overflow cup in the chamber for holding a liquid pool, a. pipe extending slidably through a liquid sealing means at the bottom of the chamber for supporting the cup therein, said pipe being connected with the enclosed system to supply liquid therefrom to the overflow cup, adjusting means engaging the pipe below the chamber for vertically adjusting the position of the overflow cup and thereby the level of the liquid pool with respect to the chamber, a hydrometer floating freely in the pool, and a window in said chamber through which the position of the hydrometer may be viewed.

2. A device responsive to changes in the density enclosed system, comprising a closed chamber, an overflow cup in the chamber for maintaining a liquid pool therein, a vertically adjustable pipe extending through the bottom of the chamber for supporting the cup therein and connected with the enclosed system to supply liquid therefrom to the overflow cup, a hy-' drorneter floating freely in the pool, a baflie in the bottom of the cup for preventing the flow of liquid from the pipe into the cup from disturbing the position of the hydrometenand a window in the chamber through which the position of the hydrometer may be viewed.

GEORGE M. CROFT. 

